Arthromelodes speciosus, Yin, 2022

Yin, Zi-Wei, 2022, The Batrisini of Tibet: unveiling an enigmatic ant-loving beetle diversity at Earth’s “ Third Pole ” (Coleoptera, Staphylinidae, Pselaphinae), Zootaxa 5111 (1), pp. 1-211 : 60-62

Arthromelodes speciosus sp. nov.

( Figs 25 , 79B , 90 )

Chinese common name: ŁƟnjà甲

Type material ( 1 ex.). HOLOTYPE: CHINA: ♂, ‘ China: Xizang, Gyirong County, Gyirong Valley , slope nr. Jifu Vill., 28°22’37”N, 85°19’41”E, 2400–2700 m, 22.vi.2021, Z. Peng, Z. Yin & W. Zhang leg., ƱẪU喀NJ吉PW 吉ė村ṉữ山坡 ’ ( SNUC).

Diagnosis. Male. Body length over 2.5 mm. Head sub-rectangular at base; vertex with deep transverse sulcus between antennal tubercles and long mediobasal carina, vertexal foveae moderately large and asetose; antenna elongate, lacking modifications; antennomeres 1–7 each slightly elongate, 8 shortest sub-moniliform, 9 strongly modified, 10 asymmetric, 11 much shorter than 9 and 10 combined. Pronotum enlarged, distinctly broader than head. Discal stria of elytron thin and shallow, extending posteriorly to approximately apical 1/6 of elytral length. Metaventrite densely setose admesally. Fore and hind legs simple, mesotrochanter with small ventral tubercle, mesotibia moderately thickened, with tiny apical protuberance. Abdomen lacking modifications, with large tergite 1 (IV) longer than tergites 2–4 (V–VII) combined. Aedeagus strongly asymmetric, ventral stalk elongate and dilated at apically, dorsal lobe extremely elongate and strongly bent downwards apically, parameres reduced and forming single membranous structure.

Description. Male. Body ( Fig. 25A ) length 2.57 mm; color reddish-brown, tarsi and mouthparts lighter. Dorsal surface of body covered with dense, moderately long pubescence.

Head ( Fig. 25B ) sub-rectangular at base, slightly wider than long, length 0.54 mm, width across eyes 0.57 mm; vertex finely punctate, with moderately large, asetose vertexal foveae (dorsal tentorial pits), with deep, slightly curved transverse sulcus between antennal tubercles, mediobasal carina extending from near head base anteriorly to sulcus, antennal tubercles weakly prominent; frons almost flat, confluent with clypeus; clypeus with smooth surface, its anterior margin carinate and moderately raised; ocular-mandibular carina complete, carina branched below eye, extended ventrally and then anteriorly to posteroventral articulation of mandible. Venter with small gular foveae (posterior tentorial pits) in single pit, with distinct median carina extending from fovea anteriorly to mouthparts. Compound eyes prominent, composed of approximately 25 large ommatidia. Antenna 1.36 mm long, with modified antennomeres 9 and 10 ( Fig. 25C ); antennomere 1 thick, subcylindrical, 2–7 each elongate, 8 smallest, sub-moniliform, much shorter and narrower than 7, 9 strongly dilated, with large apicomesal projection, 10 asymmetric, with oblique nasal margin, 11 largest, much shorter than 9 and 10 combined, sub-conical.

Pronotum ( Fig. 25B ) enlarged, much wider than head (width of pronotum / head) and slightly wider than long, length 0.61 mm, width 0.66 mm, widest at middle; lateral margins moderately expanded and rounded; disc weakly convex, finely punctate, with median longitudinal sulcus approximately as long as semicircular lateral sulci in dorsal view; lacking median antebasal fovea, with complete, deep transverse antebasal sulcus connecting lateral antebasal foveae; outer and inner pair of basolateral foveae distinct. Prosternum with anterior part slightly longer than coxal part, with small lateral procoxal foveae; hypomeral ridge present at basal 1/2, extending from base to middle of anterior part, with punctiform lateral antebasal hypomeral pit; margin of coxal cavity weakly carinate.

Elytra much wider than long, length 0.90 mm, width 0.69 mm, constricted at bases; each elytron with two large basal foveae, lacking subbasal fovea; humeral prominence barely visible; discal stria extending from outer basal fovea to apical 1/6 of elytral length; small subhumeral fovea present, thin marginal stria extending posteriorly from fovea to posterior margin of elytron.

Mesoventrite short, demarcated from metaventrite by ridged anterior edges of impressed areas where large, setose lateral mesocoxal foveae situated at mesal margins, with pair of admesal carinae; setose median mesoventral foveae broadly separated, lateral mesoventral foveae large and setose, not forked internally. Metaventrite slightly impressed at middle, with pair of setose lateral metaventral foveae, admesal areas strongly convex, densely setose; posterior margin with small and narrow split at middle.

Legs elongate, fore and hind legs simple. Procoxa with exceptionally elongate seta at base. Mesotrochanter with small ventral tubercle, mesotibia with tiny, indistinct tubercle at apex.

Abdomen as broad as elytra, widest at lateral margins of tergite 1 (IV), length 0.82 mm, width 0.87 mm, lacking modifications. Tergite 1 (IV) longer than tergites 2–4 (V–VII) combined; broadly separated mediobasal fovea and one pair of basolateral foveae separating basal sulcus, with pair of short discal carinae; tergites 2 and 3 (V and VI) each short, tergite 4 (VII) approximately as long as 2 and 3 combined along middle, tergites 2–4 (V–VII) each with one pair of small basolateral foveae, tergite 5 (VIII) semicircular, posterior margin roundly emarginate at middle. Sternite 2 (IV) with large mediobasal foveae and large basolateral sockets, with setose basal impression laterally, with pair of basolateral carinae; midlength of sternite 2 (IV) approximately as long as sternites 3–5 (V–VII) combined, 3–5 each with one pair of tiny basolateral foveae, sternite 6 (VIII) transverse, posterior margin almost straight, sternite 7 (IX) ( Fig. 25D ) slightly oval, moderately sclerotized, apical margin rounded, with long setae scattered along apical margin.

Aedeagus ( Fig. 25E, F ) 0.62 mm long, strongly asymmetric; median lobe with enlarged basal capsule and elongate foramen, lacking basoventral projection, ventral stalk long and laterally broad; dorsal lobe extremely elongate and gradually narrowing from middle towards apex, apical portion strongly curved downwards, with pointed apex; parameres reduced to single membranous structure.

Female. Unknown.

Comparative notes. The new species belongs to the A. championi group by sharing an extremely elongate endophallus of the aedeagus that is strongly curved apically. It is close to A. championi by the similar placement of the antennal modifications. The relatively enlarged pronotum and the uniquely modified male antennomeres 9 and 10 lead to a quick separation of the new species from A. championi .

Distribution. Gyirong County, Tibet, SW China ( Figs 79B , 90 ).

Etymology. The specific epithet ‘ speciosus (good-looking, beautiful)’ is a Latin adjective referring to the modification of male antennal clubs.

Figures

FIGURE 25. Morphology of Arthromelodes speciosus sp. nov., male. A. Dorsal habitus. B. Head and pronotum. C. Antennomeres 9–11. D. Sternite 7 (IX). E, F. Aedeagus, lateral (F), lateral (E) and ventral (F). Scale bars: 0.5 mm in A; 0.3 mm in B; 0.2 mm in C, E, F; 0.1 mm in D.

FIGURE 79. Distribution of Tibetan Batrisini. A. Arthromelodes markam sp. nov. (circle), A. monba sp. nov. (triangle) and A. nepaeformis sp. nov. (square). B. A. nepaeformis sp. nov. (circle), A. songxiaobini sp. nov. (triangle) and A. speciosus sp. nov. (square). C. A. torus sp. nov. (circle), A. zhangmu sp. nov. (triangle) and A. zhentangensis sp. nov. (square).

FIGURE 90. Environment of and collecting sites at Gyirong Valley. A. General environment of the valley. B. A slope dominated by conifers along the valley. C. Zhong Peng searching pselaphines under the bark of a fallen trunk.